Christy 發問於 科學及數學數學 · 1 十年 前

easy maths!!!

The difference between two numbers is 24. If twice the smaller number is subtracted from 3/4 of the greater number, the difference is 3. Find the greater number.

Bobby saved a fixed amount of money every day. He finds that the price of a model is $70 more than his savings in 5 days or $10 more than his savings in 9 days. How much does he save each day?

Donna buys some $2 stamps and some $5 stamps. If she spends %54 altogether and gets 15 stamps, how many $2 stamps dpes she buy?

1 個解答

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  • 1 十年 前
    最佳解答

    1) Let x be the greater number and (x-24)be&am p;am p;nb sp;the smaller number

    (3x/4) -2(x-24) = 3

    3x - 8(x-24) = 12

    3x - 8x + 192 =12

    -5x = -180

    x= 36

    The greater number is 36.

    2) Let $x be the amount that he saves each day

    5x +70 = 9x+10

    4x = 60

    x = 15

    He saves $15 each day.

    3) Let the number of $2stamps be x-stamps and number of $5stamps be y-stamps.

    x+y=15 ...(1)

    2x+5y=54 ...(2)

    (1) --- y=15-x ...(3)

    Sub. (3) into (2)

    2x+5(15-x)=54

    2x+75-5x=54

    -3x=-21

    x=7

    Therefore Donna buy 7-$2stamps.

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